TWI841242B - Awireless communication method and an apparatus implementable in a first multi-link device - Google Patents

Abstract

A wireless communication method, comprising: enabling, by a first multi-link device (MLD), an enhanced multi-link single-radio (EMLSR) mode; and establishing, by the first MLD, concurrent target wake time (TWT) agreements with a second MLD on multiple links including at least a first link and a second link of a plurality of links, wherein the establishing of the concurrent TWT agreements comprises: transmitting, by a first station (STA) affiliated with the first MLD, a TWT request to a first peer STA affiliated with the second MLD, the TWT request containing a TWT element that comprises a Link Identifier (ID) Bitmap subfield indicating the multiple links on which the concurrent TWT agreements are requested to be established; and receiving, by the first STA, a TWT response from the first peer STA, the TWT response containing another TWT element that comprises another Link ID Bitmap subfield indicating the multiple links on which the concurrent TWT agreements are agreed to be established.

Description

Wireless communication method and device implemented in a first multi-link device

The present disclosure relates generally to wireless communications, and more particularly to Enhanced Multi-Link Single-Radio (EMLSR) Target Wake Time (TWT) operation in wireless communications.

Unless otherwise stated herein, the methods described in this section are not prior art to the scope of the claims listed below and are not included in this section as prior art.

In wireless local area networks (WLANs) according to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 specification, concurrent TWT agreements involve establishing multiple TWT agreements on more than one link between an Access Point (AP) Multi-Link Device (MLD) and a non-AP MLD, with the TWT Service Periods (SP) of the multiple TWT agreements overlapping in time. An AP MLD may not establish concurrent TWT agreements for a single-radio non-AP MLD unless the single-radio non-AP MLD has EMLSR mode enabled (in which case the AP MLD may establish concurrent TWT agreements with the single-radio non-AP MLD). However, the details of the TWT operation between an AP MLD and a non-AP MLD are still to be further defined. Therefore, a solution is needed for EMLSR TWT operation in wireless communications.

The following summary is illustrative only and is not intended to be limiting in any way. That is, the following summary is provided to introduce the concepts, key points, benefits, and advantages of the novel and non-obvious technologies described herein. Selected implementations are further described below in the detailed description. Therefore, the following invention content is not intended to identify the necessary characteristics of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

In one aspect, the present disclosure provides a wireless communication method, which may include: a first multi-link device (MLD) enables an enhanced multi-link single radio (EMLSR) mode; and the first multi-link device and a second MLD establish a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links; wherein the establishment of the concurrent TWT protocol includes: a first station (STA) attached to the first MLD sends a TWT request to a first peer STA attached to the second MLD, and the TWT request is sent to the first peer STA attached to the second MLD. The WT request includes a TWT element, which includes a link identification (ID) bitmap subfield, and the link ID bitmap subfield indicates multiple links requested for establishing a concurrent TWT protocol; a TWT response is received from the first peer STA through the first STA, and the TWT response includes another TWT element, and the other TWT element includes another link ID bitmap subfield, and the other link ID bitmap subfield indicates multiple links on which it is agreed to establish a concurrent TWT protocol.

In another aspect, the present disclosure provides an apparatus implemented in a first multi-link device (MLD), which may include: a transceiver configured to communicate wirelessly with a second MLD; and a processor coupled to the transceiver, wherein the processor is configured to perform the following operations: enable an enhanced multi-link single radio (EMLSR) mode; and establish a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links via the transceiver and the second MLD; wherein the establishing of the concurrent TWT protocol includes: as a first station (STA) attached to the first MLD, sending a wireless communication to an attached station; The first peer STA belonging to the second MLD sends a TWT request, which includes a TWT element, and the TWT element includes a link identification (ID) bitmap subfield, and the link ID bitmap subfield indicates multiple links requested for establishing a concurrent TWT protocol; as the first STA, the TWT response is received from the first peer STA, and the TWT response includes another TWT element, and the other TWT element includes another link ID bitmap subfield, and the other link ID bitmap subfield indicates multiple links on which it is agreed to establish a concurrent TWT protocol.

It is worth noting that although the description provided herein may be in the context of certain radio access technologies, networks, and network topologies (e.g., Wi-Fi), the concepts, schemes, and any variants/derivatives presented may be implemented in and used for other types of radio access technologies, networks, and network topologies, such as, but not limited to, Bluetooth, ZigBee, Fifth Generation (5G)/New Radio (NR), Long Term Evolution (LTE), LTE-Advanced, LTE-Advanced Pro, Internet of Things (IoT), Industrial Internet of Things (IIoT), and Narrowband Internet of Things (NB-IoT). Therefore, the scope of the present disclosure is not limited to the examples described herein.

Detailed embodiments and implementations of the claimed subject matter are disclosed herein. However, it should be understood that the disclosed embodiments and implementations are merely illustrative of the claimed subject matter that may be embodied in various forms. However, the disclosure may be implemented in many different forms and should not be construed as limited to the exemplary embodiments and implementations set forth herein. Rather, these exemplary embodiments and implementations are provided so that the description of the disclosure is thorough and complete and will fully convey the scope of the disclosure to those having ordinary knowledge in the art. In the following description, details of well-known features and techniques may be omitted to avoid unnecessary ambiguity in the presented embodiments and implementations. Overview

Implementations according to the present disclosure involve various techniques, methods, schemes and/or solutions related to EMLSR TWT operations in wireless communications. According to the present disclosure, many possible solutions can be implemented individually or jointly. That is, although these possible solutions may be described separately below, two or more of these possible solutions may be implemented in one combination or another.

FIG1 shows an example network environment 100 in which various solutions and schemes according to the present disclosure may be implemented. FIG2-FIG6 show examples of implementations of various proposed schemes in the network environment 100 according to the present disclosure. The following description of various proposed schemes refers to FIG1-FIG6.

1 , a network environment 100 may include a first MLD (MLD 110) and a second MLD (MLD 120) that perform wireless communication in a plurality of links (e.g., link 1, link 2, and link 3) or in a plurality of frequency bands according to one or more IEEE 802.11 standards. Each of the MLD 110 and the MLD 120 may be used as an AP MLD or a non-AP MLD. For example, the MLD 110 may be used as a non-AP MLD including a plurality of virtual STAs operating within the MLD 110, and the MLD 120 may be used as an AP MLD including a plurality of virtual APs operating within the MLD 120. Alternatively, the MLD 110 may be used as an AP MLD including a plurality of virtual APs operating within the MLD 110, and the MLD 120 may be used as a non-AP MLD including a plurality of virtual STAs operating within the MLD 120. By way of example and not limitation of the present disclosure, in FIG. 1 , the MLD 110 is shown as being attached to a plurality of APs or non-AP STAs (e.g., STA 1 and STA 2) and the MLD 120 is shown as being attached to a plurality of APs or non-AP STAs (e.g., STA' 1 and STA' 2). It is worth noting that although a certain number of STAs (e.g., two) are shown as being attached to each of MLD 110 and MLD 120, in actual implementation, the number N of STAs attached to each of MLD 110 and MLD 120 and the number of corresponding links between MLD 110 and MLD 120 may be the same or different. Under various proposed schemes according to the present disclosure, MLD 110 and MLD 120 may be configured to perform EMLSR TWT operations in wireless communications according to various proposed schemes described herein. It is worth noting that even though each of the various proposed schemes may be described separately below, the various proposed schemes may be implemented separately or may be selected to be implemented jointly (e.g., two or more proposed schemes are implemented together).

Under the current IEEE specification, with respect to the EMLSR process, a non-AP MLD (e.g., MLD 110) may operate in EMLSR mode on a specific group of enabled links (including one or more enabled links) between the non-AP MLD and an associated AP MLD (e.g., MLD 120). The specific group of enabled links (including one or more enabled links) to which the EMLSR mode is applied may be referred to as an EMLSR link. An EMLSR link is indicated in an EMLSR link bitmap subfield of an EML control field of an Enhanced Multi-Link (EML) operation mode notification frame by setting the bit positions of the EMLSR link bitmap subfield to 1. For EMLSR mode enabled in a single-radio non-AP MLD (e.g., MLD 110), when a STA operating on one of the EMLSR links and attached to the non-AP MLD is in the awake state, one or more STAs attached to the non-AP MLD operating on the link corresponding to the EMLSR Link Bitmap subfield bit position 0 may be in the dormant state. In addition, an MLD with dot11EHTEMLSROptionImplemented equal to "true" may set the EML Capabilities Present subfield to 1 and may also set the EMLSR Support subfield of the Common Info field of the Basic Multi-Link element in all management frames (except authentication frames) including the Basic Multi-Link element to 1. On the one hand, an MLD with dot11EHTEMLSROptionImplemented equal to "false" and dot11EHTEMLMROptionImplemented equal to "true" can set the EML Capabilities Present subfield to 1 and can also set the EMLSR Support subfield of the EML Capabilities subfield to 0. On the other hand, an MLD with dot11EHTEMLSROptionImplemented equal to "false" and dot11EHTEMLMROptionImplemented equal to "false" can set the EML Capabilities Present subfield to 0.

Regarding the execution of the EMLSR process, when a non-AP MLD (e.g., MLD 110) whose dot11EHTEMLSROptionImplemented is equal to "true" wants to operate in EMLSR mode on the EMLSR link, a STA attached to the non-AP MLD can send an EML operation mode notification frame to an AP attached to an AP MLD (e.g., MLD 120) whose dot11EHTEMLSROptionImplemented is equal to "true" and set the EMLSR mode subfield of the EML control field of the EML operation mode notification frame to 1. In addition, the AP attached to the AP MLD that receives the EML operation mode notification frame from the STA attached to the non-AP MLD can send an EML operation mode notification frame to one of the multiple STAs attached to the non-AP MLD within a timeout interval indicated in a transition timeout subfield of an EML capability subfield of a basic multi-link element as an acknowledgment of the EML operation mode notification frame sent by the STA attached to the non-AP MLD, wherein the timeout interval starts from the end of a physical-layer Protocol Data Unit (PPDU) sent by the AP attached to the AP MLD. After the STA attached to the non-AP MLD successfully sends an EML operation mode notification frame on one of the EMLSR links, the non-AP MLD may operate in the EMLSR mode, and the STAs on the other links of the EMLSR link may transition to the active mode after the transition delay indicated in the transition timeout subfield in the EML capability subfield of the basic multi-link element, or the STAs on the other links of the EMLSR link may transition to the active mode immediately after receiving the EML operation mode notification frame from one of the APs operating on the EMLSR link and attached to the AP MLD. In addition, the STA on one of the other links of the EMLSR link may not send a frame with the power management subfield set to 1 before receiving the EML operation mode notification frame from the AP attached to the AP MLD or before the timeout expires.

Regarding the disabling EMLSR process, when a non-AP MLD (e.g., MLD 110) whose dot11EHTEMLSROptionImplemented is equal to "true" wants to disable the EMLSR mode, a STA attached to the non-AP MLD can send an EML operation mode notification frame to an AP attached to an AP MLD (e.g., MLD 120) whose dot11EHTEMLSROptionImplemented is equal to "true" and set the EMLSR mode subfield of the EML control field of the EML operation mode notification frame to 0. Accordingly, the AP attached to the AP MLD, which receives the EML operation mode notification frame from the STA attached to the non-AP MLD, can send an EML operation mode notification frame to one of the STAs attached to the non-AP MLD within the timeout interval indicated in the transition timeout subfield of the EML capability subfield of the basic multi-link element as an acknowledgment of the EML operation mode notification frame sent by the STA attached to the non-AP MLD, and the timeout interval starts from the end of the physical layer protocol data unit (PPDU) sent by the AP attached to the AP MLD. After the STA attached to the non-AP MLD successfully sends an EML operation mode notification frame on one of the EMLSR links, the non-AP MLD may disable the EMLSR mode and the STAs on the other links of the EMLSR link may transition to a power-save mode after a transition delay indicated in a transition timeout subfield in an EML capability subfield of a basic multi-link element, or the STAs on the other links of the EMLSR link may transition to a power-save mode immediately after receiving an EML operation mode notification frame from one of the APs operating on the EMLSR link and attached to the AP MLD. In addition, the STA on one of the other links of the EMLSR link may not send a frame with a power management subfield set to 0 before receiving an EML operation mode notification frame from the AP attached to the AP MLD or before the timeout expires.

As described below, when a non-AP MLD (e.g., MLD 110) is operating in EMLSR mode and an AP MLD (e.g., MLD 120) supports EMLSR mode, certain conditions may apply. For example, the non-AP MLD can listen on the EMLSR link by waking up its attached STA corresponding to the EMLSR link. The listening operation may include clear channel assessment (CCA) and receiving an initial control frame of a frame exchange initiated by the AP MLD. In addition, the initial control frame of the frame exchange may be sent in an orthogonal frequency division multiplexing (OFDM) PPDU or non-high throughput (non-HT) replicated PPDU format using a rate of 6 Mbps, 12 Mbps, or 24 Mbps. In addition, the initial control frame may be a Multi-User Request-To-Send (MU-RTS) trigger frame or a Buffer Status Report Poll (BSRP) trigger frame, and the reception of MU-RTS and BSRP trigger frames may be mandatory for a non-AP MLD in EMLSR mode. The number of response spatial streams for a BSRP trigger frame may be limited to one. In addition, a non-AP MLD may indicate a delay duration in the EMLSR Padding Delay subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element. In addition, an AP attached to an AP MLD that initiates a frame exchange with a non-AP MLD on one of the EMLSR links may start a frame exchange by sending an initial control frame to the non-AP MLD using the above restrictions, including the above rates, formats, and frame types. After receiving the initial control frame of the frame exchange until the frame exchange is completed, a STA attached to a non-AP MLD listening on the corresponding link may send or receive frames on the link where the initial control frame was received, but may not send or receive frames on other EMLSR links. Depending on the spatial stream capabilities, operation mode, and link switching delay of the STA attached to the non-AP MLD, the STA may be able to receive PPDUs sent using more than one spatial stream on the link where the initial control frame was received after the short inter-frame space (SIFS) after the end of the response frame transmission of the initial control frame request. During the frame exchange, other APs attached to the AP MLD may not send frames to other STAs attached to the non-AP MLD on other EMLSR links.

When any of the conditions described below are met, the non-AP MLD may switch back to snooping operation on the EMLSR link after the time indicated in the EMLSR Transition Delay subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element, which may be defined as the end of a frame exchange. For example, the Medium Access Control (MAC) layer of a STA belonging to a non-AP MLD that receives an initial control frame does not receive a PHY-RXSTART.indication primitive within a timeout interval of aSIFSTime+aSlotTime+aRxPHYStartDelay, where aSIFSTime+aSlotTime+aRxPHYStartDelay starts from the end of a PPDU sent by the STA of the non-AP MLD as a response to a frame recently received from an AP belonging to an AP MLD, or where aSIFSTime + aSlotTime + aRxPHYStartDelay starts from the end of a PPDU containing a frame for the STA received from an AP belonging to an AP MLD that does not require immediate confirmation. In addition, the MAC layer of the STA attached to the non-AP MLD that receives the initial control frame receives the PHY-RXSTART.indication primitive during the timeout period aSIFSTime+aSlotTime+aRxPHYStartDelay and the STA attached to the non-AP MLD does not detect any of the following frames (a)-(e) in the PPDU corresponding to PHY-RXSTART.indication. Frames (a)-(e) include: (a) an individually addressed frame in which the RA (Receiver Address) is equal to the MAC address of the STA attached to the non-AP MLD, (b) a trigger frame in which a user information field is addressed to the STA attached to the non-AP MLD, (c) a CTS-to-self frame in which the RA is equal to the MAC address of the AP attached to the AP MLD, (d) a multi-STA block acknowledgment frame (BlockAck) in which one per-association IDentifier (AID) traffic identifier (TID) is addressed to the STA attached to the non-AP MLD, and (e) a Neighbor Discovery Protocol (NDP) announcement frame in which a STA information field is addressed to the STA attached to the non-AP MLD. Finally, a STA that receives an initial control frame and is attached to a non-AP MLD does not respond to the most recently received frame from an AP that is attached to an AP MLD, which is required to respond immediately after a SIFS.

As described below, when a non-AP MLD (e.g., MLD 110) is operating in EMLSR mode and an AP MLD (e.g., MLD 120) supports EMLSR mode, other conditions may apply. For example, if an AP attached to an AP MLD wants to continue frame exchange with a STA attached to a non-AP MLD and the AP does not receive a response frame from the STA for the most recently transmitted frame that requires an immediate response after a SIFS, the AP may transmit another initial control frame addressed to the STA attached to the non-AP MLD before the Transmission Network Allocation Vector (TXNAV) timer expires. When a STA of a non-AP MLD initiates a Transmission Opportunity (TXOP), the non-AP MLD can switch back to the listening operation on the EMLSR link after the TXOP ends and after the duration indicated by the EMLSR Transition Delay subfield. In addition, only a STA operating on one of the EMLSR links and attached to the non-AP MLD can initiate a frame exchange with the AP MLD.

FIG. 2 illustrates an example scenario 200 under a proposed scheme for EMLSR TWT operation according to the present disclosure. Part (A) of FIG. 2 illustrates that STA 1 and STA 2 attached to MLD 110 perform EMLSR TWT operation with MLD 120 on link 1 and link 2, respectively. Due to the concurrent TWT protocol, the TWT SPs of the TWT protocols on link 1 and link 2 may overlap in time. During the TWT SP, STA 1 may receive a BSRP trigger frame on link 1, and in response, send a Buffer Status Report (BSR) before receiving data from a corresponding AP (e.g., AP1) attached to MLD 120. Meanwhile, due to EMLSR, STA 2 will not receive any content on link 2 during the TWT SP. Part (B) of Figure 2 shows an example format of a single TWT Information Element (IE) (interchangeably referred to herein as a "TWT element") under the proposed scheme. The TWT element may include a TWT parameter set having a plurality of parameters, such as the plurality of parameters shown in part (B) of Figure 2, including a link information parameter, which may include a link identification (ID) bitmap subfield (e.g., occupying fifteen bits B0 to B14) and a synchronous TWT request subfield (e.g., occupying bit B15). A predefined value (e.g., 1) in the synchronous TWT request subfield may indicate that the plurality of links indicated by the link ID bitmap subfield require alignment of the TWT SPs on all of these plurality of links; a different value (e.g., 0) in the synchronous TWT request subfield may indicate other situations.

Under the proposal regarding the TWT protocol according to the present disclosure, a STA attached to an MLD (e.g., MLD 110) can indicate the link requested for establishing the TWT protocol in the link ID bitmap subfield (if any) of the TWT element in a soliciting TWT request sent to another STA attached to a peer MLD (e.g., MLD 120). When only one link is indicated in the link ID bitmap subfield of the TWT element, it means that STAs attached to the same MLD can request a single TWT protocol and the STA operates on the indicated link. The target wakeup time field of the TWT element can refer to the timing synchronization function (TSF) time of the link indicated by the TWT element. In addition, under the proposed scheme, a STA affiliated with a peer MLD (e.g., MLD 120 or MLD 110) that receives a TWT request (the TWT request includes a link ID bitmap subfield in the TWT element) may respond with a TWT response that also indicates the link in the link ID bitmap field of its TWT element. The link in the TWT element in the TWT response (if any) may be the same as the link indicated in the TWT element of the requesting TWT request.

Under the proposed scheme for negotiation of the TWT protocol according to the present disclosure, during the negotiation of the TWT protocol, a TWT requesting STA attached to one MLD (e.g., MLD 110 or MLD 120) and a TWT responding STA attached to another MLD (e.g., MLD 120 or MLD 110) may include a plurality of TWT elements, and each link ID bitmap subfield in each TWT element indicates a different link in the same TWT setup frame. The TWT parameters provided by each TWT element may be applied and may refer to the corresponding link indicated in the TWT element. In addition, a STA attached to a peer MLD that receives a TWT request containing multiple TWT elements may respond with a TWT response that indicates a link in the link ID bitmap field of the TWT element. The link in the TWT element in the TWT response may be the same as the link indicated in the TWT element of the TWT request.

FIG3 shows an example scenario 300 under the proposed scheme of EMLSR TWT operation according to the present disclosure. Part (A) of FIG3 shows that STA 1 and STA 2 of MLD 110 perform EMLSR TWT operation with MLD 120 on link 1 and link 2, respectively. Part (B) of FIG3 shows an example format of the TWT Teardown frame Action field. Under the proposed scheme, for STA1 that is attached to a non-AP MLD (e.g., MLD 10) that has EMLSR mode enabled and has established concurrent TWT protocols with a peer MLD (e.g., MLD 120) on multiple links, the concurrent TWT protocols (e.g., for Link 1 and Link 2) may be terminated by the non-AP MLD sending a TWT teardown frame before switching back from the EMLSR mode to the single radio mode (e.g., on Link 1). Referring to part (A) of FIG. 3 , the TWT teardown frame may terminate the TWT protocol of STA2 that is attached to the non-AP MLD (e.g., on Link 2). Ultimately, the TWT protocol may exist only on a single link (e.g., on Link 1) rather than on multiple links simultaneously.

Refer to part (B) of Figure 3, which shows the format of the TWT Teardown frame Action field. Specifically, the TWT Flow field of the TWT teardown frame may include multiple subfields, for example, including a TWT flow identifier subfield, a link ID bitmap present subfield, a reserved subfield, a negotiation type subfield, a teardown all TWT subfield, and a teardown link ID subfield (or as shown in Figure 3, referred to as a "link ID bitmap subfield"). The demolition link ID bitmap subfield may exist when the value of the link ID bitmap exists subfield is equal to 1; otherwise, the demolition link ID bitmap subfield may not exist. The demolition link ID bitmap subfield may indicate that the link of the concurrent TWT protocol needs to be terminated due to the TWT demolition frame sent by the STA attached to the MLD. The value of bit position i of the demolition link ID bitmap subfield is 1, which may mean that the relevant link terminates the concurrent TWT protocol due to the TWT demolition frame sent by the STA attached to the MLD. Conversely, a value of 0 in bit position i of the Teardown Link ID Bitmap subfield may mean that the link associated with Link ID i is not a link for which concurrent TWT protocols need to be terminated due to a TWT Teardown frame sent by a STA attached to the MLD. That is, the TWT protocol on each link indicated by a value of 1 in the Teardown Link ID Bitmap subfield will be terminated or otherwise torn down. In addition, under the proposed scheme, the STA may set the Teardown All TWT subfield to 1 to indicate that the TWT Teardown frame will terminate or otherwise tear down all TWT protocols on all links. Alternatively, the Teardown All TWT subfield may be set to 0 to indicate other situations.

Under the proposed scheme for EMLSR TWT operation according to the present disclosure, a STA attached to an MLD can negotiate an individual TWT protocol with another STA attached to another MLD, but there are some exceptions. One exception may be that a STA attached to an MLD can indicate the link (one or more) for requesting to establish the TWT protocol in the link ID bitmap subfield (if present) of the TWT element of the TWT request. If only one link is indicated in the link ID bitmap subfield of the TWT element, it means that the STA attached to the same MLD requests a single TWT protocol and the STA operates on the indicated link. The target wakeup time field of the TWT element can refer to the timing synchronization function (TSF) time of the link indicated by the TWT element. Another exception may be that a STA attached to an MLD may indicate the link(s) for which the TWT protocol is being requested to be torn down in the Link ID Bitmap subfield of the TWT Teardown frame (if present). If only one link is indicated in the Link ID Bitmap subfield of the TWT Teardown frame, it means that the STAs attached to the same MLD requested to tear down a single TWT protocol and the STA is operating on the indicated link.

FIG4 illustrates an example scenario 400 under a proposed scheme for EMLSR TWT operation according to the present disclosure. According to the proposed scheme, a STA attached to an MLD may negotiate an individual TWT protocol with another STA attached to another MLD, with some exceptions. As shown in FIG4 , one exception may be that if the link ID bitmap subfield (or referred to as the "teardown link ID bitmap subfield") does not exist in the TWT teardown frame, the MLD may send a TWT teardown frame on the link requesting the teardown of the TWT protocol. As shown in FIG4 , since a TWT teardown frame without a link ID bitmap subfield may be sent by STA 2 on link 2, the TWT protocol on link 2 (but not on link 1) may be terminated or otherwise torn down. Another exception may be when the MLD wants to terminate all TWTs established on all links. The MLD may set the bit value of the bit position in the link bitmap subfield corresponding to all links established by the MLD to 1.

Under the proposed scheme for negotiating the wake-up target beacon transmission time (TBTT) and wake-up interval according to the present disclosure, a TBTT-scheduled STA that intends to operate in power saving mode can send a TWT request to a TBTT-scheduling AP, which identifies the wake-up TBTT of the first beacon frame and the wake-up interval between subsequent beacon frames that the STA wants to receive. Under the proposed scheme, a TWT request may include: (a) a negotiation type subfield equal to 1 and a TWT set command field set to either proposed TWT or required TWT, (b) the requested first wakeup TBTT included in the target wakeup time field, (c) the requested wakeup interval between consecutive TBTTs in the TWT wakeup interval mantissa and TWT wakeup interval exponent fields, (d) the requested TBTT wakeup duration in the Nominal Minimum TWT Wake Duration field, and (e) all other fields that may be retained in the TWT element. Under the proposed scheme, an AP that receives a TWT request from a STA with a scheduled TBTT with a negotiation type subfield value of 1 can respond by including a TWT response of accepting TWT, backing up TWT, or rejecting TWT in the TWT set command field. In the case of an Accept TWT, the TWT Response may also contain: (a) a Negotiation Type subfield equal to 1, (b) the assigned first wakeup TBTT in the Target Wake Time field, (c) the assigned wakeup interval between consecutive TBTTs in the TWT Mantissa and TWT Exponent fields, (d) the assigned TBTT wakeup duration in the Nominal Minimum TWT Wake Duration field, and (e) all other fields that may be retained in the TWT element.

Under the proposed scheme, after successfully completing the negotiation, the TBTT-scheduled STA can enter the sleep state, and if there are no other conditions requiring the STA to remain awake, the STA is in power saving mode until the STA's TSF matches the next negotiated wake-up TBTT. The TBTT-scheduled STA can be in the awake state to listen to the beacon frame sent in the negotiated wake-up TBTT, and can operate according to the rules for TWT-scheduled STA. In the case that the TBTT-scheduled STA receives a beacon frame from the AP that schedules the TBTT at or after the TBTT, if there are no other conditions requiring the STA to remain awake, the TBTT-scheduled STA can enter the sleep state until the next wake-up TBTT. A TBTT-scheduled STA may enter the sleep state after the nominal minimum TBTT wakeup duration starting from the TBTT start time, provided that there are no other conditions requiring the STA to remain awake. In addition, any STA that is a party to an established wakeup TBTT protocol may tear down the wakeup TBTT protocol by following the teardown procedure and setting the Negotiation Type subfield in the TWT Teardown frame to 1.

According to the scheme for EMLSR TBTT negotiation proposed in the present disclosure, a STA attached to a non-AP MLD (eg, MLD 110) operating in EMLSR mode may negotiate a wakeup TBTT and a wakeup interval with an AP attached to an AP MLD (MLD 120). When a first STA (e.g., STA 1) attached to a non-AP MLD negotiates a wakeup TBTT and a wakeup interval with a first AP (e.g., AP 1) attached to an AP MLD to receive a beacon frame on one of the EMLSR links, a second AP (e.g., AP 2) attached to the AP MLD may terminate a frame exchange initiated with a second STA (e.g., STA 2) attached to the non-AP MLD in another EMLSR link for at least one EMLSR transition delay (indicated in the EMLSR transition delay subfield) before the first AP attached to the same AP MLD schedules the transmission of the beacon frame in the negotiated TBTT. Alternatively or additionally, when a first STA (e.g., STA 1) attached to a non-AP MLD negotiates a wakeup TBTT and a wakeup interval with a first AP (e.g., AP 1) attached to an AP MLD to receive a beacon frame on one of the EMLSR links, a second STA (e.g., STA 2) attached to the non-AP MLD that initiates a frame exchange in another EMLSR link may end the TXOP by at least one EMLSR transition delay (indicated in the EMLSR transition delay subfield) before the first STA attached to the same non-AP MLD receives a beacon frame in the negotiated TBTT. Illustrative Implementation

FIG5 illustrates an example system 500 including at least an example device 510 and an example device 520 according to an implementation of the present disclosure. Each of the device 510 and the device 520 can perform various functions to implement the schemes, techniques, processes and methods described herein related to EMLSR TWT operations in wireless communications, including the above-described designs, concepts, schemes, systems and methods described above and the processes described below with respect to various proposed designs, concepts, schemes, systems and methods described above. For example, the device 510 can be an example implementation of the MLD 110, and the device 520 can be an example implementation of the MLD 120.

Each of device 510 and device 520 may be part of an electronic device, such as, but not limited to, a portable or mobile device, a wearable device, a wireless communication device, or a computing device. For example, each of device 510 and device 520 may be implemented in a smart phone, a smart watch, a personal digital assistant, a digital camera, or a computing device such as a tablet, a laptop, or a notebook. Each of device 510 and device 520 may also be part of a machine-type device, which may be an IoT device such as a fixed or static device, a home device, a wired communication device, or a computing device. For example, each of device 510 and device 520 may be implemented in a smart thermostat, a smart refrigerator, a smart door lock, a wireless speaker, or a home control center. When implemented in or as a network device, device 510 and/or device 520 may be implemented in a network node (eg, an AP in a WLAN).

In some implementations, each of the device 510 and the device 520 may be implemented in the form of one or more integrated circuit (IC) chips, such as but not limited to one or more single-core processors, one or more multi-core processors, one or more reduced instruction set computing (RISC) processors, or one or more complex instruction set computing (CISC) processors. As an example, each of the device 510 and the device 520 may include at least some of the components shown in FIG. 5, for example, may include the processor 512 and the processor 522 shown in FIG. 5, respectively. Each of device 510 and device 520 may also include one or more other components that are not related to the solution proposed in the present disclosure (for example, an internal power supply, a display device and/or a user interface device), and therefore, for simplicity, such components (one or more) of device 510 and device 520 are not shown in Figure 5 and will not be described below.

In one aspect, each of processor 512 and processor 522 may be implemented in the form of one or more single-core processors, one or more multi-core processors, one or more RISC processors, or one or more CISC processors. That is, even though the singular term "a processor" is used herein to refer to processor 512 and processor 522, according to the present invention, each of processor 512 and processor 522 may include multiple processors in some implementations and may include a single processor in other implementations. On the other hand, each of processor 512 and processor 522 can be implemented in the form of hardware (and, optionally, firmware) having electronic components, including, for example, but not limited to, one or more transistors, one or more diodes, one or more capacitors, one or more resistors, one or more inductors, one or more memristors and/or one or more varactors, which are configured and arranged to achieve specific purposes in accordance with the present disclosure. In other words, in at least some embodiments, each of processor 512 and processor 522 is a dedicated machine that is specially designed, arranged and configured to perform specific tasks, including tasks related to EMLSR TWT operations in wireless communications in accordance with various embodiments of the present invention.

In some implementations, the device 510 may further include a transceiver 516 coupled to the processor 512. The transceiver 516 may be capable of wirelessly transmitting and receiving data. In some implementations, the device 520 may further include a transceiver 526 coupled to the processor 522. The transceiver 526 may include a transceiver capable of wirelessly transmitting and receiving data. The transceiver 516 of the device 510 and the transceiver 526 of the device 520 may communicate with each other through one or more of a plurality of links link 1 to link N (e.g., a first link and a second link), where N is a positive integer greater than 1.

In some embodiments, the device 510 may also include a memory 514 coupled to the processor 512 and accessible by the processor 512 and capable of storing data therein. In some embodiments, the device 520 may also include a memory 524 coupled to the processor 522 and accessible by the processor 522 and capable of storing data therein. Each of the memory 514 and the memory 524 may include a type of random access memory (RAM), such as dynamic RAM (DRAM), static RAM (SRAM), thyristor RAM (T-RAM) and/or zero capacitor RAM (Z-RAM). Alternatively or additionally, each of the memory 514 and the memory 524 may include a type of read-only memory (ROM), such as mask ROM, programmable ROM (PROM), erasable programmable ROM (EPROM), and/or electrically erasable programmable ROM (EEPROM). Alternatively or additionally, each of the memory 514 and the memory 524 may include a type of non-volatile random access memory (NVRAM), such as flash memory, solid-state memory, ferroelectric RAM (FeRAM), magnetoresistive RAM (MRAM), and/or phase change memory.

Each of the device 510 and the device 520 may be a communication entity capable of communicating with each other using various proposed schemes according to the present disclosure. For illustrative purposes and not limitation, the following provides a description of the capabilities of the device 510 as the MLD 110 which may be a non-AP MLD, and the device 520 as the MLD 120 which may be an AP MLD. It is noted that although the example implementations described below are provided in the context of a WLAN, they may also be implemented in other types of networks.

Under the proposed scheme for EMLSR TWT operation in wireless communication according to the present disclosure, the processor 512 of the device 510 as the first MLD (e.g., MLD 110) can enable the EMLSR mode (e.g., to make the MLD 110 enter the EMLSR mode). In addition, the processor 512 can establish a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links with the device 520 as the second MLD (e.g., MLD 120) via the transceiver 516. When establishing the concurrent TWT protocol, the processor 512 can perform certain operations. For example, the processor 512 may send a TWT request as a first STA attached to a first MLD to a first peer STA attached to a second MLD, the TWT request including a TWT element, the TWT element including a link ID bitmap subfield, the link ID bitmap subfield indicating a plurality of links requested for establishing a concurrent TWT protocol. In addition, the processor 512 may receive a TWT response as a first STA from the first peer STA, the TWT response including another TWT element including another link ID bitmap subfield, the other link ID bitmap subfield indicating a plurality of links on which a concurrent TWT protocol is agreed to be established.

In some implementations, the TWT element may also include a synchronized TWT request subfield. In this case, all TWT SPs on multiple links may be aligned in response to a predefined value set in the synchronized TWT request subfield.

In some implementations, the processor 512 may terminate the concurrent TWT protocol with the second MLD by sending a TWT teardown frame before switching from EMLSR mode to single radio mode.

In some implementations, when terminating a concurrent TWT protocol, the processor 512 may terminate the concurrent TWT protocol by terminating the TWT protocol on the second link in response to a TWT teardown frame indicating termination of the TWT protocol on the second link.

In some implementations, the TWT teardown frame may include at least a link ID bitmap existence subfield, which indicates whether a teardown link ID bitmap subfield (as described above, or simply referred to as a "link ID bitmap subfield") exists in the TWT teardown frame. In this case, in response to the link ID bitmap existence subfield indicating that the teardown link ID bitmap subfield exists in the TWT teardown frame, the teardown link ID bitmap subfield may indicate the termination of one or more applicable links. Alternatively or additionally, the TWT teardown frame may include at least the teardown of all TWT subfields. In this case, termination may include termination of all concurrent TWT protocols on multiple links in response to removal of predefined values set in all TWT subfields.

In some implementations, when terminating a concurrent TWT protocol, the processor 512 may, as a first STA, send a TWT teardown frame to a first peer STA on a first link to indicate the termination of the corresponding TWT protocol on at least one of the multiple links. Alternatively or additionally, when terminating a concurrent TWT protocol, the processor 512 may, as a second STA attached to a first MLD, send a TWT teardown frame to a second peer STA attached to a second MLD on a second link, wherein the TWT teardown frame indicates the termination of the corresponding TWT protocol on the second link without including a teardown link ID bitmap subfield.

In some embodiments, the processor 512 may perform additional operations. For example, the processor 512 may negotiate a TBTT and a wakeup interval with a first peer STA attached to a second MLD as a first STA when in EMLSR mode. In addition, the processor 512 may receive one or more beacon frames from the first peer STA on one or more EMLSR links of a plurality of links as a first STA and according to the negotiated TBTT and wakeup interval. In some embodiments, the first MLD may be a non-AP MLD, and the second MLD may be an AP MLD and the first peer STA may be a first AP.

In some implementations, upon receiving one or more beacon frames, processor 512 and processor 522 may perform certain operations. For example, processor 522 may, as a second AP attached to a second MLD, terminate a frame exchange initiated with a second STA attached to a first MLD on another link of one or more EMLSR links by at least one EMLSR transition delay before the first AP sends each of the one or more beacon frames in the negotiated TBTT. In addition, processor 512 may, as a second STA, terminate a TXOP on the other link by at least one EMLSR transition delay before the first STA receives each of the one or more beacon frames in the negotiated TBTT. In this case, the EMLSR transition delay may be indicated in the EMLSR transition delay subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element in the Management Frame transmitted between the first MLD and the second MLD .

Fig. 6 shows an example process 600 according to an embodiment of the present disclosure. Process 600 can represent an aspect of the design, concept, scheme, system and method for realizing the above-mentioned various proposals. More specifically, process 600 can represent an aspect of the proposed concept and scheme related to the EMLSR TWT operation in the wireless communication according to the present disclosure. Process 600 can include one or more operations, actions or functions, as illustrated in one or more of blocks 610 and 620 and sub-blocks 622 and 624. Although the blocks in the figure are illustrated as discrete blocks, each block of process 600 can be divided into other blocks, combined into fewer blocks, or eliminated, depending on the desired implementation. In addition, the blocks/sub-blocks of process 600 can be executed in the order shown in Fig. 6, or executed in different orders. In addition, one or more blocks/sub-blocks of process 600 may be performed repeatedly or repeatedly. Process 600 may be implemented by or in device 510 and device 520 and any variations thereof. For purposes of illustration only and without limitation of scope, process 600 is described in the context of device 510 and device 520 being respectively an MLD 110 (e.g., non-AP MLD) and an MLD 120 (e.g., peer STA MLD or AP MLD) in a wireless network (e.g., WLAN) according to one or more IEEE 802.11 standards. Process 600 may begin at block 610.

At 610 , process 600 may include processor 512 of device 510 as a first MLD (eg, MLD 110 ), enabling EMLSR mode (eg, causing MLD 110 to enter EMLSR mode). Process 600 may proceed from 610 to 620 .

At 620, the process 600 may include the processor 512 establishing a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links with the device 520 as a second MLD (e.g., MLD 120) via the transceiver 516. When establishing the concurrent TWT protocol, as shown in 622 and 624, the process 600 may include the processor 512 performing certain operations.

At 622, process 600 may include processor 512, as a first STA attached to a first MLD, sending a TWT request to a first peer STA attached to a second MLD, the TWT request including a TWT element, the TWT element including a link ID bitmap subfield, the link ID bitmap subfield indicating a plurality of links requested for establishing a concurrent TWT protocol. Process 600 may proceed from 622 to 624.

At 624, process 600 may include the processor 512 receiving, as the first STA, a TWT response from the first peer STA, the TWT response comprising another TWT element, the other TWT element comprising another link ID bitmap subfield, the other link ID bitmap subfield indicating a plurality of links on which concurrent TWT protocols are agreed to be established.

In some implementations, the TWT element may also include a synchronized TWT request subfield. In this case, all TWT SPs on multiple links may be aligned in response to a predefined value set in the synchronized TWT request subfield.

In some implementations, process 600 may further include processor 512 terminating the concurrent TWT protocol with the second MLD by sending a TWT teardown frame before switching from EMLSR mode to single radio mode.

In some embodiments, when terminating a concurrent TWT protocol, process 600 may include the processor 512 terminating the concurrent TWT protocol by terminating the TWT protocol on the second link in response to a TWT teardown frame indicating termination of the TWT protocol on the second link.

In some implementations, the TWT teardown frame may include at least a link ID bitmap presence subfield, the link ID bitmap presence subfield indicating whether a teardown link ID bitmap subfield exists in the TWT teardown frame. In this case, in response to the link ID bitmap presence subfield indicating that the teardown link ID bitmap subfield exists in the TWT teardown frame, the teardown link ID bitmap subfield may indicate the termination of one or more applicable links. Alternatively or additionally, the TWT teardown frame may include at least the teardown of all TWT subfields. In this case, in response to a predetermined value set in the teardown all TWT subfields, the termination may include terminating concurrent TWT protocols on all multiple links.

In some embodiments, when terminating a concurrent TWT protocol, the process 600 may include the processor 512, as a first STA, sending a TWT teardown frame to a first peer STA on a first link to indicate the termination of the corresponding TWT protocol on at least one of the multiple links. Alternatively or additionally, when terminating a concurrent TWT protocol, the process 600 may include the processor 512, as a second STA attached to a first MLD, sending a TWT teardown frame to a second peer STA attached to a second MLD on a second link, wherein the TWT teardown frame indicates the termination of the corresponding TWT protocol on the second link without including a teardown link ID bitmap subfield.

In some embodiments, the process 600 may also include the processor 512 performing additional operations. For example, the process 600 may include the processor 512 negotiating a TBTT and a wakeup interval with a first peer STA attached to a second MLD as a first STA when in EMLSR mode. In addition, the process 600 may include the processor 512 receiving one or more beacon frames from the first peer STA on one or more EMLSR links of a plurality of links as a first STA and according to the negotiated TBTT and wakeup interval. In some embodiments, the first MLD may be a non-AP MLD, and the second MLD may be an AP MLD and the first peer STA may be a first AP.

In some implementations, upon receiving one or more beacon frames, process 600 may include processor 512 performing certain operations. For example, process 600 may include a second AP attached to a second MLD terminating a frame exchange initiated with a second STA attached to a first MLD on another link of one or more EMLSR links for at least one EMLSR transition delay before the first AP transmits each of the one or more beacon frames at a negotiated TBTT. Additionally, process 600 may include the second STA terminating a TXOP on the other link for at least one EMLSR transition delay before the first STA receives each of the one or more beacon frames at the negotiated TBTT. In this case, the EMLSR transition delay may be indicated in the EMLSR transition delay subfield of the EML Capability subfield in the Common Information field of the Basic Multilink Element in the Management Frame transmitted between the first MLD and the second MLD .

The subject matter described herein sometimes illustrates different components contained within or connected to different other components. It is to be understood that the architectures so depicted are merely examples, and that many other architectures that can achieve the same functionality can actually be implemented. Conceptually, any arrangement of multiple components that achieve the same functionality is effectively "associated" to achieve the desired functionality. Therefore, any two components that are combined to achieve a particular functionality can be considered to be "associated" with each other to achieve the desired functionality, regardless of the architecture or intermediate components. Similarly, any two components so associated can also be considered to be "operably connected" or "operably coupled" to each other to achieve the desired functionality, and any two components that can be so associated can also be considered to be "operably coupled to each other" to achieve the desired functionality. Specific examples of operable coupling include, but are not limited to, physically mateable and/or physically interacting components and/or wirelessly interactable and/or wirelessly acting components and/or logically interacting and/or logically interactable components.

In addition, with respect to any plural and/or singular used herein, a person skilled in the art having ordinary knowledge can convert the plural to the singular and/or the singular to the plural from the perspective of appropriate context and/or application. The various singular/plural descriptions herein are for clarity only.

In addition, one having ordinary skill in the art will understand that, generally, the terms used herein, especially the terms in the appended claims, such as the body of the appended claims, are generally intended to be "open" terms, for example, the term "including" should be interpreted as "including but not limited to", the term "having" should be interpreted as "having at least", and the plural term "including" should be interpreted as "including but not limited to", and one having ordinary skill in the art will further understand that if it is intended to introduce a specific quantity into the description in the claims, such intention will be explicitly stated in the claims, and in the absence of such a statement, no such intention exists. For example, to aid understanding, the claims appended below may include the introductory phrases "at least one" and "one or more" to introduce the claims. However, the use of these phrases should not be interpreted as implying that a claim statement introduced by the indefinite article "a" or "an" is limited to any particular claim statement containing only one implementation of such a statement, even if the same claim statement includes the introductory phrases "one or more" or "at least one", and indefinite articles such as "a" or "an", such as "a" and/or "an" should be interpreted as "at least one" or "one or more"; this interpretation also applies to claims statements using definite articles to introduce claims. In addition, even if an introductory claim scope statement explicitly refers to a specific quantity, one of ordinary skill in the art will recognize that such statement should be interpreted to mean at least the cited quantity, e.g., the simple statement "two statements", without other modifiers, means at least two statements, or two or more statements. In addition, in those cases where terms similar to “at least one of A, B, and C, etc.” are used, such a structure is generally intended to be understood by a person having ordinary knowledge in the art to which the term is applied, for example, “a system having at least one of A, B, and C” includes but is not limited to having only a single A, a single B, a single C, A and B together, A and C together, B and C together, and/or A, B, and C together, etc., and in those cases where terms similar to “at least one of A, B, or C, etc.” are used, such a structure is generally intended to be understood by a person having ordinary knowledge in the art to which the term is applied, for example, “a system having at least one of A, B, or C” includes but is not limited to having only a single A, a single B, a single C, A and B together, A and C together, B and C together, and/or A, B, and C together, etc. Those skilled in the art will further understand that virtually any separating word and/or phrase presenting two or more alternative terms, whether appearing in the specification, patent application or drawings, should be understood to include one of the terms, either of the terms, or both of the terms. For example, the phrase "A or B" will be understood to include the possibility of "A" or "B" or "A and B".

It can be understood from the foregoing that various implementations of the present disclosure have been described herein for illustrative purposes, and various modifications may be made without departing from the scope and spirit of the present disclosure. Therefore, the various implementations disclosed herein are not intended to be limited to the true scope and spirit indicated by the attached patent application scope.

100: Network environment 110,120: Multilink device 200,300,400: Example scenario 500: Example system 510,520: Device 512,522: Processor 514,524: Memory 516,526: Transceiver 600: Example process 610,620: Frame 622,624: Subframe

The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated into and constitute a part of the present disclosure. The accompanying drawings illustrate implementations of the present disclosure and are used together with the specification to explain the principles of the present disclosure. It is understood that the drawings are not necessarily drawn to scale because some components may be shown as being out of proportion to the size in the actual implementation in order to clearly illustrate the concepts of the present disclosure. Figure 1 shows an example network environment 100 in which various solutions and schemes according to the present disclosure can be implemented. Figure 2 shows an example scenario 200 under a proposed scheme for EMLSR TWT operation according to the present disclosure. Figure 3 shows an example scenario 300 under a proposed scheme for EMLSR TWT operation according to the present disclosure. Figure 4 shows an example scenario 400 under a proposed scheme for EMLSR TWT operation according to the present disclosure. FIG. 5 illustrates an example system 500 including at least an example device 510 and an example device 520 according to an implementation of the present disclosure. FIG. 6 illustrates an example process 600 according to an implementation of the present disclosure.

600: Example process

610,620: frame

622,624: Subframe

Claims (18)

A wireless communication method, comprising: a first multi-link device (MLD) enabling an enhanced multi-link single radio (EMLSR) mode; and the first MLD and a second MLD establishing a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links; wherein the establishment of the concurrent TWT protocol comprises: a first station (STA) attached to the first MLD sending a TWT request to a first peer STA attached to the second MLD, the TWT request comprising a TWT element, the TWT element comprising a link identification (ID) bitmap subfield, the link ID The bitmap subfield indicates a plurality of links requested for establishing a concurrent TWT protocol; receiving a TWT response from the first peer STA through the first STA, the TWT response including another TWT element, the another TWT element including another link ID bitmap subfield, the another link ID bitmap subfield indicating a plurality of links agreed to establish a concurrent TWT protocol thereon; wherein the method further includes: the first MLD sends a TWT teardown frame to terminate the concurrent TWT protocol with the second MLD before switching from the EMLSR mode to the single radio mode. A wireless communication method as described in claim 1, wherein the TWT element further includes a synchronous TWT request subfield, and wherein in response to a predefined value set in the synchronous TWT request subfield, all TWT service periods (SPs) on the plurality of links are aligned. The wireless communication method as described in claim 1, wherein terminating the concurrent TWT protocol comprises: terminating the concurrent TWT protocol by terminating the TWT protocol on the second link in response to the TWT teardown frame indicating the termination of the TWT protocol on the second link. A wireless communication method as described in claim 1, wherein the TWT demolition frame includes at least a link ID bitmap existence subfield, the link ID bitmap existence subfield indicates whether a demolition link ID bitmap subfield exists in the TWT demolition frame, and wherein in response to the link ID bitmap existence subfield indicating that the demolition link ID bitmap subfield exists in the TWT demolition frame, the demolition link ID bitmap subfield indicates one or more links to which the termination applies. A wireless communication method as described in claim 1, wherein the TWT teardown frame at least includes tearing down all TWT subfields, and wherein in response to a predetermined value set in the teardown all TWT subfields, the termination includes terminating concurrent TWT protocols on all the multiple links. The wireless communication method as described in claim 1, wherein terminating the concurrent TWT protocol comprises: the first STA sends the TWT teardown frame to the first peer STA on the first link to indicate the termination of the corresponding TWT protocol on at least one of the multiple links. The wireless communication method as described in claim 1, wherein terminating the concurrent TWT protocol comprises: the second STA attached to the first MLD sends the TWT teardown frame to the second peer STA attached to the second MLD on the second link, wherein the TWT teardown frame indicates the termination of the corresponding TWT protocol on the second link without including the teardown link ID bitmap subfield. The wireless communication method as described in claim 1 further includes: the first STA attached to the first MLD negotiates a target beacon frame transmission time (TBTT) and a wake-up interval with a first peer STA attached to the second MLD when in the EMLSR mode; and the first STA receives one or more beacon frames from the first peer STA on one or more EMLSR links of the plurality of links according to the negotiated TBTT and the wake-up interval; wherein the first MLD includes a non-AP MLD, and the second MLD includes an AP MLD and the first peer STA includes a first AP. The wireless communication method as described in claim 8 further includes: before the first AP sends each of one or more beacon frames in the negotiated TBTT, the second AP attached to the second MLD ends the frame exchange initiated with the second STA attached to the first MLD on another link of one or more EMLSR links by at least one EMLSR transition delay; and before the first STA receives each of one or more beacon frames in the negotiated TBTT, the second STA ends the TXOP on the other link by at least one EMLSR transition delay; wherein the EMLSR transition delay is indicated in the EMLSR transition delay subfield of the EML capability subfield in the common information field of the basic multi-link element in the management frame transmitted between the first MLD and the second MLD. An apparatus implemented in a first multi-link device (MLD), comprising: a transceiver configured to communicate wirelessly with a second MLD; and a processor coupled to the transceiver, wherein the processor is configured to perform the following operations: enable an enhanced multi-link single radio (EMLSR) mode; and establish a concurrent TWT protocol on a multi-link including at least a first link and a second link of a plurality of links via the transceiver and the second MLD; wherein the establishment of the concurrent TWT protocol comprises: as a first station (STA) attached to the first MLD, sending a TWT request to a first peer STA attached to the second MLD, the TWT request comprising a TWT element, the TWT element comprising A link identification (ID) bitmap subfield, the link ID bitmap subfield indicating a plurality of links requested for establishing a concurrent TWT protocol; as the first STA receives a TWT response from the first peer STA, the TWT response includes another TWT element, the other TWT element includes another link ID bitmap subfield, the other link ID bitmap subfield indicating a plurality of links agreed to establish a concurrent TWT protocol thereon; wherein the processor is further configured to perform the following operations: Sending a TWT teardown frame by the transceiver to terminate the concurrent TWT protocol with the second MLD before switching from the EMLSR mode to the single radio mode. The device of claim 10, wherein the TWT element further comprises a synchronous TWT request subfield, and wherein in response to a predetermined value set in the synchronous TWT request subfield, all TWT service periods (SPs) on the plurality of links are aligned. The device as claimed in claim 10, wherein terminating the concurrent TWT protocol comprises: terminating the concurrent TWT protocol by terminating the TWT protocol on the second link in response to the TWT teardown frame indicating the termination of the TWT protocol on the second link. The device as claimed in claim 10, wherein the TWT demolition frame includes at least a link ID bitmap existence subfield, the link ID bitmap existence subfield indicates whether a demolition link ID bitmap subfield exists in the TWT demolition frame, and wherein in response to the link ID bitmap existence subfield indicating that the demolition link ID bitmap subfield exists in the TWT demolition frame, the demolition link ID bitmap subfield indicates one or more links to which the termination applies. The apparatus of claim 10, wherein the TWT teardown frame comprises at least tearing down all TWT subfields, and wherein in response to a predetermined value set in the teardown all TWT subfields, the termination comprises terminating concurrent TWT protocols on all of the plurality of links. The device as described in claim 10, wherein terminating the concurrent TWT protocol comprises: sending the TWT teardown frame to the first peer STA on the first link as the first STA to indicate the termination of the corresponding TWT protocol on at least one of the plurality of links. The apparatus of claim 10, wherein terminating the concurrent TWT protocol comprises: sending the TWT teardown frame to a second peer STA attached to the second MLD on the second link as a second STA attached to the first MLD, wherein the TWT teardown frame indicates the termination of the corresponding TWT protocol on the second link without including a teardown link ID bitmap subfield. The apparatus of claim 10, wherein the processor is further configured to perform the following operations: as the first STA attached to the first MLD, when in the EMLSR mode, negotiate a target beacon frame transmission time (TBTT) and a wakeup interval with a first peer STA attached to the second MLD; and as the first STA, receiving one or more beacon frames from the first peer STA on one or more EMLSR links of the plurality of links according to the negotiated TBTT and the wakeup interval; wherein the first MLD includes a non-AP MLD, and the second MLD includes an AP MLD and the first peer STA includes a first AP. The apparatus of claim 17, wherein before the first AP transmits each of the one or more beacon frames in the negotiated TBTT, a second AP attached to the second MLD terminates a frame exchange initiated by a second STA attached to the first MLD on another link of the one or more EMLSR links for at least one EMLSR transition delay; and the processor is further configured to perform the following operations: The TA terminates the TXOP on the other link as the second STA for at least one EMLSR transition delay before receiving each of one or more beacon frames at the negotiated TBTT; wherein the EMLSR transition delay is indicated in the EMLSR transition delay subfield of the EML capability subfield in the common information field of the basic multi-link element in the management frame transmitted between the first MLD and the second MLD.